1. Field of the Invention
The present invention generally relates to an uplink transmission method and apparatus in an inter-evolved Node B (eNB) inter-duplex carrier aggregation system and, more particularly, to a method and apparatus for transmitting uplink signals including feedback for use in scheduling at different eNBs without intermodulation especially when the User Equipment (UE) is connected to an inter-duplex inter-eNB system where the eNBs are cooperating very slowly.
2. Description of the Related Art
Mobile communication systems have been developed in order to provide subscribers with voice communication services on the move. With the rapid advance of technology, mobile communication systems have evolved to support high speed data communication services as well as standard voice communication services. However, the limited resources and user requirements for higher speed services in current mobile communication systems have spurred the evolution to more advanced mobile communication systems.
In order to meet such requirements, the 3rd Generation Partnership Project (3GPP) is standardizing Long Term Evolution-Advanced (LTE-A) as one of the next generation mobile communication technologies. LTE-A is a high speed packet-based communication technology which offers up to 1 Gbps in downlink. In order to accomplish this, several schemes are being discussed: one increases the number of eNBs and another uses multiple frequency bands per UE.
When the UE connects to more than one eNB, if cooperation among the eNBs is delayed, it is necessary for the UE to transmit feedback for use in scheduling at each of the respective eNBs rather than one representative eNB. When two eNBs to which the UE has connected operate on different frequency bands in different duplex configurations, the UE has to perform uplink transmission to the different eNBs, and this may cause inter-modulation problems.
There is therefore a need for a method and apparatus for transmitting uplink signals to eNBs operating on different frequency bands without causing inter-modulation problems.